Technical Field
The present invention relates to a resin gear device with a resin lubricating grease composition applied and to an actuator provided with the resin gear device such as a multi-stage gear device. Here, the present invention particularly relates to a resin gear device used in an actuator for an air-conditioning (“Heating Ventilation and Air Conditioning”; hereinafter referred to as “HVAC”) system for installation in a vehicle. In this application, the resin gear device means a device having at least one resin gear, i.e., at least one resin-made gear.
Related Art
In the current energy-saving boom of the automobile industry, the development of hybrid and electric automobiles has become imperative. By using a motor as the drive source, hybrid and electric automobiles have achieved great improvements in quietness compared to conventional gasoline automobiles. Thus, the conventional noise level in an actuator for a vehicle interior HVAC system is no longer compatible with the high level of quietness of hybrid and electric automobiles, and a need has arisen for an actuator whose noise level is further reduced.
Therefore, as one measure for reducing the noise of a gear device of an actuator or the like, gears made of a resin (hereinafter also referred to simply as “plastic gears”) have begun to replace gears made of metal.
Plastic gears and sliding members made of a resin (plastic) are advantageous in that they are light, not easily affected by chemicals, do not rust, generate only a small operational noise level, and are self-lubricating. In addition, they are also advantageous in that they are suited to mass production and can be manufactured at low cost.
As a raw material for the plastic gears described above, a polyacetal (POM) resin, a polyamide (PA) resin, and a polybutylene terephthalate (PBT) resin are generally used. It is also known that the use of elastic gears made of a polyurethane rubber, an elastomeric material, or the like can achieve a noise reducing effect.
Meanwhile, in order to impart lubricity to the surfaces of the resin members such as plastic gears or the like, there are various proposals for grease compositions that are used on the engaging parts and the bearing part of a plastic gear in the same manner as in a metal gear. For example, the following grease compositions have been proposed: a grease composition including a base oil, a thickening agent, a fluorochemical surfactant, and a styrene block copolymer (JP 2007-297422 A), an oil non-separating lubricant composition in which the separation of oil is prevented by using a specific polymer material (JP 2002-327188 A), and a grease composition in which the separation of oil is suppressed under high temperature conditions (JP 2012-177105 A).